The World Wide Web (“web”) uses the client-server model to communicate information between clients and servers. Web servers are coupled to the Internet and respond to document requests from web clients. Web clients (e.g., web “browsers”) are programs that allow a user to simply access web documents located on web servers.
An example of a client-server system interconnected through the Internet may include a remote server system interconnected through the Internet to a client system. The client system may include conventional components such as a processor, a memory (e.g., RAM), a bus which coupled the processor and memory, a mass storage device (e.g., a magnetic hard disk or an optical storage disk) coupled to the processor and memory through an I/O controller and a network interface, such as a conventional modem. The server system also may include conventional components such as a processor, memory (e.g., RAM), a bus which coupled the processor and memory, a mass storage device (e.g., a magnetic or optical disk) coupled to the processor and memory through an I/O controller and a network interface, such as a conventional modem.
To define the addresses of resources on the Internet, Uniform Resource Locator (URL) system are used. A URL is a descriptor that specifically defines a type of Internet resource and its location. To access an initial web document, the user enters the URL for a web document into a web browser program. Then, a request is made by a client system, such as a router or other network device, and is sent out over the network to a web server. Thus, the web browser sends a request to the server that has the web document using the URL. The web server responds to the request and sends the desired content back over the network to the requester. For example, the web server responds to the http request by sending the requested object to the client. In many cases, the object is a plain text (ASCII) document containing text (in ASCII) that is written in HyperText Markup Language (HTML); however, the object may be a video clip, movie or other bandwidth intensive content.
A problem with the Internet is that it has limited bandwidth resources and different points in the Internet may experience network congestion, resulting in poor performance especially for bandwidth-intensive applications. The Internet backbone is often painfully slow. The bandwidth limitation is mainly due to one or more congested links between the web server and the client. Broadband access can help in solving the first mile problem but does not help if the congestion occurs deeper in the network.
High-quality on-demand video over the Internet has been promised for a long time now. Lately, the hype has increased due to the emerging deployment of broadband access technologies like digital subscriber line (DSL), cable modems, and fixed wireless. These technologies promise to bring full motion, TV quality video to consumers and businesses. Unfortunately, early adopters of the technology quickly discovered that they still cannot get video in any reasonable quality over the network. Certainly, broadband access improves the viewing experience—some web sites targeted to broadband connected customers provide movies with slightly higher resolution. However, the video remains as jerky and fuzzy as before, synchronization with the audio is poor, and it requires often tens of seconds of buffering before starting. Nobody would seriously consider this to be an alternative to DVD or analog TV.
Providing video over the Internet is difficult because video requires huge amounts of bandwidth, even by today's standards. MPEG4-compressed NTSC-quality video, for example, uses an average data rate of 1.2 Mbits/s, with peak rates as high as 3 Mbits/s. MPEG2/DVD quality video consumes 3.7 Mbits/s on the average, with peaks up to 8 Mbits/s.
Most of today's broadband Internet links, especially those to small to medium-sized businesses (SMBs) typically provide data rates in the 100s of Kbits/s up to 2 Mbits/s. Most residences get asynchronous digital subscriber line (ADSL) technology, which is typically provisioned at approximately 1 Mbits/s for downloads from the Internet, and 128 Kbits/s for uploads. Often access links are shared among multiple users, which further reduces the bandwidth available to an individual.
While these data rates are expected to gradually increase in the long term, another phenomenon causing bandwidth shortage will remain: overprovisioning. Typically, Internet Service Providers (ISPs) overprovision their broadband links for economic reasons by a factor of ten. This means that if all their customers would use the service simultaneously, every one of those customers would get only 1/10th of the bandwidth they signed up for. While this scenario might sound unlikely, it is important to note that bandwidth will degrade during peak hours. The problem is better known from cable modems, where customers share a cable segment, but applies to all broadband access technologies.
The network backbone can also be the bottleneck. Especially backbone peering points are likely to impose low data rates, which slows down end-to-end network speed despite fast last mile technology. Even technology advances such as terabit routers, dense wave division multiplexing (DWDM), and faster transmission equipment will not help significantly if, as expected, Internet traffic continues to keep growing faster than these advances in technology.
One prior art solution to accommodate the slowness of the Internet backbone is to move content closer to individuals desiring the content. To that end, content may be cached on the carrier edge and requests for such content may be serviced from these caches, instead of the web server servicing the requests. Distributing content in this manner can require large numbers of cache memories being deployed at the carrier edge and each cache memory stores content from a number of sites. When a request is made for content from a site that has been stored in one (or more) of the cache memories that is closer (from a network proximity viewpoint) to the requester than the original website, the request is satisfied from the cache. In such a situation, the interactive experience for text and images is improved significantly only if content from the site has been stored in the cache and the individual making the request is close enough to one of the servers supporting such a cache to satisfy requests with the content stored therein. This is referred to as carrier edge caching. One provider of such a service is Akamai. Also, such an arrangement for caching content requires that the content owner and the entity caching the content enter an agreement with respect to the access for that content so that the content can be stored ahead of time. Some of the providers of a carrier edge caching service use dedicated links (e.g., via satellites) to feed web pages and embedded objects to these servers and circumvent the Internet backbone entirely. Providing carrier edge caching for high-resolution video requires a particularly large number of servers to be deployed, since the number of clients each server can handle simultaneously is very small.
While carrier edge caching takes the load off the backbone and has the potential to significantly improve the end user's experience for text and image-based content, there are two major shortcomings with this approach. First, it requires hardware infrastructure to be deployed on a giant scale. Without servers in all major ISP's point of presence (POPs) and satellite receivers in central offices (COs), caching on the carrier edge does not work effectively. To deploy and maintain this hardware infrastructure is very cost intensive. Second, the last mile access link remains the bottleneck for affordable truly high resolution video for the foreseeable future.
Thus, high-quality video-on-demand in the strongest sense of the word might be something that will not be available for a while. However, despite all these limitations, a broadband access link of 500 KBits/s can deliver more than 5 GByte of data in 24 hours, which corresponds to 8 hours of NTSC quality video, or 3 hours of DVD quality video—more than most people, especially at work, ever watch.